1. Field of the Invention
The present invention relates to an impact buffer, an impact buffering device, and an information processor having the impact buffering device.
2. Background Art
Recently, the carrying/using frequency of an information processor such as a notebook-size personal computer (hereinafter referred to as “notebook computer”) has been increased, the weight and size of the information processor have been decreased, and the portability thereof has been improved. The information processor is therefore required to withstand an impact by an unexpected drop during carrying/using it or a harsh environment such as vibration during using it on a vehicle. For instance, a hard disk drive unit (hereinafter referred to as “HDD unit”) can go out of order due to the impact of a drop to damage important data. Therefore, an information processor such as a notebook computer that is carried and used is desired to have higher impact resistance, to be further lightened in weight, and to be further downsized.
A conventional impact buffer and impact buffering device will be described hereinafter.
For instance, Japanese Patent Unexamined Publication No. H05-319347 discloses an impact buffering device having a coil spring and a viscosity resistor employing a cylinder. Thus, an impact buffering device generally has a mechanism employing a viscosity resistor that is constituted by combining a plurality of components such as a cylinder and a spring such as a coil spring.
Japanese Patent Unexamined Publication No. H10-141408 discloses an impact buffer having foam and an auxiliary cover for protecting the foam. When a foam member is used as in this impact buffer, high impact buffering performance is obtained, and the size and weight can be reduced. For reducing the size and weight of a device, use of a foam member is appropriate, hence the impact buffering performance is high and the production cost for mass production is small because of the simple structure thereof, advantageously.
Japanese Patent Unexamined Publication No. 2005-256982 discloses an example employing a foam member as an impact buffering device for protecting an HDD unit of a notebook computer. FIG. 5 is a schematic sectional view of the state where impact buffer 204 for protecting HDD unit 206 is butted and mounted on HDD unit 206 that is apt to be affected by an impact in a conventional notebook computer.
As shown in FIG. 5, the notebook computer has HDD unit 206 apt to be affected by an impact and elastic impact buffer 204 employing a foam member for protecting HDD unit 206. The notebook computer further has HDD case (box) 207 for storing HDD unit 206 and impact buffer 204.
HDD unit 206 has the following elements:                magnetic head 205;        head arm 208 mounted to rotating shaft 210;        magnetic disk (sometimes called a platter) 209 on which magnetic data is recorded; and        head arm rotation stopper 211 for fixing head arm 208 to prevent it from moving freely from a shunting position.        
Head arm rotation stopper 211 has an inertia latch structure described later. HDD unit 206 is mounted to casing 214 of the notebook computer via impact buffer 204.
The operation of HDD unit 206 includes operation where magnetic head 205 reads data recorded on magnetic disk 209 or records data on magnetic disk 209. During operation of HDD unit 206, magnetic head 205 is moved to a target position on magnetic disk 209 in a head loading state. Here, in the head loading state, a predetermined separation distance is kept from the surface of magnetic disk 209 for rotating magnetic head 205 at a high speed. Magnetic head 205 and head arm 208 during this operation are shown by broken lines in FIG. 5. During either of non-operation and operation, when HDD unit 206 is in an idling state where no access request is made, magnetic head 205 is moved into a member for shunting (not shown) that is disposed at a position separated from magnetic disk 209. Magnetic head 205 in this state is shunted to the position separated from the disk by head unloading operation. Here, the head unloading operation is performed for locking magnetic head 205 at that position. Magnetic head 205 and head arm 208 during this operation are shown by solid lines. In FIG. 5, counterclockwise arrow 232 shows a head loading direction of head arm 208, and clockwise arrow 233 shows a head unloading direction of head arm 208.
However, a complicated structure such as that of the impact buffering device discussed above is not appropriate for size and weight reduction, and the production cost and maintenance cost are apt to increase. For improving the impact buffering performance of the impact buffer or impact buffering device employing a foam member, generally, the characteristic of the foam member is improved or the foam shape such as volume and mounting area of the foam is optimized. However, further improvement of the buffering performance, further reduction of hazardous gas generated from the foam, and further weight reduction or the like of the impact buffering device are required.
When the impact buffering performance is improved, the foam volume can be enlarged, the weight of the impact buffering device can be increased in response to the enlargement, and the hazardous gas generated from the foam can be increased. Therefore, generally, high impact buffering performance and reduction of the size and weight of the device, and reduction of the amount of generated hazardous gas are mutually contradictory.
Generally, the impact buffering phenomenon can be modeled using the following equation of motionmz+cy+kx=0.
Here, z is an acceleration of a matter, y is a velocity of the matter, x is a displacement of the matter, m is a mass of the matter, c is a viscous damping coefficient of a viscous resistor, and k is a spring constant of a spring.
The impact buffering member employing a foam member such as resin foam has characteristics of both the spring and the viscous resistor. Therefore, an impact buffer having both desired spring constant (k) and viscous damping coefficient (c) must be used in response to an application. The higher viscous damping coefficient (c) is, the more impact energy is consumed in the impact buffer. However, foam having an ideal characteristic having desired spring constant (k) and viscous damping coefficient (c) is difficult to be produced in response to application. In other words, it is difficult to produce an evolutionary foam shape that exhibits high impact buffering performance. For example, the optimization of the foam shape such as the volume and mounting area of the foam has been considered, but it is difficult to exhibit a sufficient buffering performance in a limited space.
The internal structure corresponding to the dropping impact of HDD unit 206 is described with reference to FIG. 6A through FIG. 6F. In FIG. 6A through FIG. 6F, only parts receiving the impact of casing 214, HDD case 207, and impact buffer 204 are shown. FIG. 6A through FIG. 6F are schematic sectional views for describing the operations of a conventional impact buffering member, impact buffer 204, and HDD unit 206 when a user accidentally drops the notebook computer.
FIG. 6A and FIG. 6D are schematic sectional views showing a state where HDD unit 206 is dropping. FIG. 6B and FIG. 6E are schematic sectional views showing states where HDD unit 206 is tilting to the side of the center of gravity after dropping and colliding against the ground or the like. FIG. 6C and FIG. 6F are schematic sectional views showing states where the restoring force of impact buffer 204 works after HDD unit 206 drops and collides against the ground or the like.
As shown in FIG. 6A and FIG. 6D, the center-of-gravity position of HDD unit 206 is assumed to be on the right side of the center line (dashed line) of the substantially rectangular casing surface of HDD unit 206.
First, using FIG. 6A, FIG. 6B and FIG. 6C, operation when the installation space on impact buffer 204 and thickness of an elastic member are sufficient to withstand an impact by a drop is described.
As shown in FIG. 6A, thickness L1 of impact buffer 204 for protecting HDD unit 206 is assumed to be sufficient to absorb the impact by the drop of HDD unit 206. When HDD unit 206 drops toward the ground or a desk in the direction of arrow 240, casing 214 of the notebook computer collides against the ground or the desk in a short time, as shown in FIG. 6A. As a result, as shown in FIG. 6B, displacement of the center-of-gravity position of HDD unit 206 from the center line of the substantially rectangular casing surface of HDD unit 206 causes HDD unit 206 to rotate clockwise (direction of arrow 213). Impact buffer 204 sufficiently absorbs the impact. Then, as shown in FIG. 6C, the restoring force of impact buffer 204 causes HDD unit 206 to rotate counterclockwise (direction of arrow 212) to slowly restore it. At this time, the rotation of HDD unit 206 is slow, so that the head detachment (described later) does not occur.
Next, using FIG. 6D, FIG. 6E and FIG. 6F, operation when the installation space on impact buffer 204 and thickness of an elastic member are restricted is described.
As shown in FIG. 6D, thickness L2 of impact buffer 204 for protecting HDD unit 206 is assumed to be thinner than L1 and is not sufficient to absorb the impact by the drop of HDD unit 206. When HDD unit 206 drops on the ground or a desk, as shown in FIG. 6E, displacement of the center-of-gravity position of HDD unit 206 from the center line of the substantially rectangular casing surface of HDD unit 206 causes HDD unit 206 to also rotate clockwise (direction of arrow 213). HDD unit 206 cannot completely absorb the impact by the rotation, so that impact buffer 204 is crushed into a state near a rigid body. Therefore, rotation moment sharper than that in FIG. 6B occurs. A case where this rotation moment occurs in latch non-operation mode of the inertial latch structure is described hereinafter in detail.
As shown in FIG. 6E, when HDD unit 206 drops on the ground or the desk, the displacement of the center of gravity of HDD unit 206 first causes HDD unit 206 to rotate clockwise (direction of arrow 213). Impact buffer 204 cannot absorb the impact, so that the lower right corner of HDD unit 206 collides against HDD case 207. Then, the rebound of the collision and the restoring force of impact buffer 204 cause HDD unit 206 to rotate counterclockwise (direction of arrow 212). HDD unit 206 therefore rotates counterclockwise (direction of arrow 212) so as to press impact buffer 204 downward while impact buffer 204 absorbs the impact. Then, as shown in FIG. 6F, the lower left corner of HDD unit 206 collides against HDD case 207, and head arm 208 can rotate counterclockwise (direction of arrow 232) due to this impact and inertia to move from the shunting position onto magnetic disk 209.
Head arm 208 is kept in weight balance with respect to rotating shaft 210, so that only the surface dropping impact of HDD unit 206 in each plane direction acts. Therefore, when HDD unit 206 does not rotate, the rotation moment of head arm 208 does not occur, and head arm 208 does not rotate.
However, generally, the direction of the dropping impact does not become stable, and HDD unit 206 rotates in the direction responsive to the positional relationship between the landing surface and the center of gravity of HDD unit 206 during acting of the dropping impact.
Head arm 208 therefore starts to rotate relatively to HDD unit 206 due to the inertia. In other words, when the thickness of the elastic member of impact buffer 204 is not sufficient, impact buffer 204 cannot sufficiently absorb the impact by the drop. As a result, as shown in FIG. 6F, when the impact of the collision applied to HDD unit 206 is large, head arm 208 continues to rotate due to the inertia. Then, head arm 208 rotates from the shunting position in the direction of arrow 232, and can move and adhere onto magnetic disk 209.
During non-operation of HDD unit 206, head arm 208 is fixed to the shunting position with the inertial latch structure of head arm rotation stopper 211. When HDD unit 206 rotates in the direction of arrow 212, the impact received by HDD unit 206 is transferred to head arm 208 as it is. As a result, with some impact timing, the inertial latch structure of head arm rotation stopper 211 comes off, and head arm 208 starts to rotate in the direction of arrow 232. When the impact is large, head arm 208 continues to rotate due to the inertia, becomes detached from the shunting position, and moves and adheres onto magnetic disk 209. These phenomena are called head detachment.
Here, when an impact causes HDD unit 206 to rotate, the inertial latch structure latches head arm 208 to regulate the rotation before head arm 208 rotates and moves to a breakdown position.
HDD unit 206 essentially includes a structure capable of engaging a latch regardless of the direction of the rotation of HDD unit 206. When HDD unit 206 starts to rotate in the opposite direction (direction of arrow 212) after operation of the inertial latch structure, however, time lag occurs in latch operation until restart of the inertial latch structure. When head arm 208 rotates counterclockwise (direction of arrow 232) due to inertia as in FIG. 6F and the left end of HDD unit 206 collides against HDD case 207 in a short time during the time lag, the inertial latch structure does not work, the motion of head arm 208 cannot be inhibited, and head detachment occurs sometimes.
In other words, when the factors of both the rotation of the head arm and timing of non-operation of the inertial latch structure conspire, head detachment occurs disadvantageously.